1840.] SENATE— No. 36. 203 



J. 



FOOD OF PLANTS. 



"The chief source from which plants derive the materials for their 

 growth is the soil. However various the composition of the soil, it 

 consists essentially of two parts, so far as its solid constituents are con- 

 cerned. One is a certain quantity of earthy matter, such as siliceous 

 earth, clay, lime, and sometimes magnesia ; and the other is formed 

 from the remains of animal and vegetable substances, which, when 

 mixed with the former, constitute common mould. A mixture of this 

 kind moistened by rain affords the proper nourishment of plants. The 

 water, percolating through the mould, dissolves the soluble salts with 

 which it comes in contact, together with the gaseous, extractive and 

 other matters which are formed during the decomposition of the ani- 

 mal and vegetable remains. In this case it is readily absorbed by the 

 roots and conveyed as sap to the leaves, where it undergoes a process 

 of assimilation." 



" But though this is the natural process by which plants obtain the 

 greater part of their nourishment, and without which they do not arrive 

 at perfect maturity, they may live, grow, and even increase in weight, 

 when wholly deprived of nutrition from this source. In the experi- 

 ments of Saussure, sprigs of peppermint were found to vegetate in dis- 

 tilled water ; and it is well known that many plants grow when merely 

 suspended in the air. In the hot house of the botanical garden of 

 Edinburgh, for example, there are two plants, species of the fig tree, 

 the Ficus aiisti-alis and the Ficiis dustica, the latter of which has been 

 suspended for ten, and the former for nearly sixteen years, during 

 which time they have continued to send out shoots and leaves." — Tur- 

 ner's Clumistrij, p. 565. 



" There are some plants that fasten themselves and grow upon the 

 most barren rocks, deriving from the surrounding air and from rains, 

 all the nourishment required by them; of this number are the mosses, 

 the lichens, and the fleshy plants. Their growth is slow; their trans- 

 piration almost nothing, and their color remains nearly the same all 

 the year round, so that they constantly absorb water, and carbonic 

 acid ; and assimilate their constituent principles." — Chaptal, p. 92. 



